1. Field of the Invention
This invention relates to a position switch for detecting the operating position of a select lever for use in switching ranges of an automatic transmission.
2. Description of the Related Art
One known conventional position switch of the sort stated above is provided with four signal lines of L1-L4 so that, as shown in FIG. 6, on and off signals are outputted to the signal lines in such predetermined combinations as to correspond to the respective operating positions of a select lever. In this case, as shown in FIG. 6, xe2x80x9c1xe2x80x9d represents an ON signal and xe2x80x9c0xe2x80x9d an OFF signal. The ON signal is applied to the following signal lines: to the signal line of L3 in the parking range position of xe2x80x9cPxe2x80x9d; to the signal line of L4 in the reverse range position of xe2x80x9cRxe2x80x9d; to the signal line of L2 in the neutral range position of xe2x80x9cNxe2x80x9d; to the signal lines of L1, L2 and L3 in the range position of xe2x80x9cDxe2x80x9d for automatic transmission; to the signal lines of L1, L2 and L4 in the range position of xe2x80x9c3xe2x80x9d for automatic transmission up to three speeds; to the signal lines of L1, L3 and L4 in the range position of xe2x80x9c2xe2x80x9d for holding second speed; to the signal lines of L2, L3 and L4 in the range position of xe2x80x9c1xe2x80x9d for holding first speed; to the signal lines of L3 and L4 in the position of xe2x80x9cZ1xe2x80x9d between xe2x80x9cPxe2x80x9d and xe2x80x9cRxe2x80x9d; to the signal lines of L2 and L4 in the position of xe2x80x9cZ2xe2x80x9d between xe2x80x9cRxe2x80x9d and xe2x80x9cNxe2x80x9d; to the signal lines of L1 and L2 in the position of xe2x80x9cZ3xe2x80x9d between xe2x80x9cNxe2x80x9d and xe2x80x9cDxe2x80x9d; and to the signal lines of L1, L2, L3 and L4 in the position of xe2x80x9cZ4xe2x80x9d between xe2x80x9cDxe2x80x9d and xe2x80x9c3xe2x80x9d, in the position of xe2x80x9cZ5xe2x80x9d between xe2x80x9c3xe2x80x9d and xe2x80x9c2xe2x80x9d and in the position of xe2x80x9cZ6xe2x80x9d between xe2x80x9c2xe2x80x9d and xe2x80x9c1xe2x80x9d.
When the signal line of L1 is broken in the aforementioned conventional position switch, combinations of the on and off signals in the respective positions of xe2x80x9cZ4xe2x80x9d, xe2x80x9cZ5xe2x80x9d and xe2x80x9cZ6xe2x80x9d turn out to be the same combination of xe2x80x9c0, 1, 1 and 1xe2x80x9d as that in the range position of xe2x80x9c1xe2x80x9d. When the signal line of L1 is broken at the time the range xe2x80x9cDxe2x80x9d is switched to the range xe2x80x9c3xe2x80x9d, the behavior of the vehicle may be badly affected by the establishment of first speed stage during high-speed traveling because the position of xe2x80x9cZ4xe2x80x9d is misjudged to be the range position of xe2x80x9c1xe2x80x9d.
In view of the foregoing problems, the present invention is intended to provide a position switch so arranged that the behavior of a vehicle is prevented from being badly affected by the misjudgment made on a switching range when a signal line is broken.
In order to solve the foregoing problems according to the present invention, there is provided a position switch for detecting the operating position of a select lever for use in switching ranges of an automatic transmission, the position switch which includes a plurality of signal lines and which is arranged so that on and off signals may be applied to the signal lines in such predetermined combinations as to correspond to the respective operating positions of the select lever. Combinations of on and off signals corresponding to the respective positions of the select lever are set in the whole operating position of the select lever in such a manner that even when a signal in any one of the signal lines out of the plurality of signal lines remains to be an off signal, the combination of on and off signals is prevented from coinciding with a combination of on and off signals corresponding to any operating position other than operating positions adjacent to each of the operation positions.
According to the present invention, the operating position of the select lever includes range positions of xe2x80x9cPxe2x80x9d, xe2x80x9cRxe2x80x9d, xe2x80x9cNxe2x80x9d, xe2x80x9cDxe2x80x9d, xe2x80x9c3xe2x80x9d, xe2x80x9c2xe2x80x9d, xe2x80x9c1xe2x80x9d and the like, and intermediate positions xe2x80x9cZ1xe2x80x9d-xe2x80x9cZ6xe2x80x9d and the like between the range positions. The operating position adjacent to each range position is the intermediate position between each range position and the adjoining range position. The operating positions adjacent to each intermediate position are the range positions with the intermediate position held therebetween.
Even when any one of the signal lines to which the on signal is applied is broken and causes the signal of the signal line to become the off signal in each range position, the range position is not misjudged to be any other range position but only misjudged to be the adjoining intermediate position according to the present invention. Similarly, a range position that may be misjudged in each intermediate position is only what is adjacent to the intermediate position and this prevents the behavior of a vehicle from being badly affected thereby.